Posted by Anonymous on Wednesday, February 22, 2012 at 4:36pm.
Given that cos2x=7/12 and "270 equal or < 2x equal or < 360", find sinx.
Please help and Thank you
Trig Help - Reiny, Wednesday, February 22, 2012 at 5:06pm
In these type of quesstions it usually asks for the "exact" value of ....
cos 2x = 7/12
cos 2x = 1 - 2sin^2 x
2 sin^2 x = 1 - cos 2x = 1 - 7/12 = 5/12
sin^2 x = 5/24
sin x = ± √(5/24)
but 270 < 2x ≤ 360
135 ≤ x ≤ 180 ---> x in in I or II, so
sinx = +√5/√24 = √30/12
Trig Help - Anonymous, Wednesday, February 22, 2012 at 5:49pm
how did you get the ã30/12?
Trig Help - Anonymous, Wednesday, February 22, 2012 at 6:15pm
when you rationalize the denominator you times both top and bottom by sqrt(6) only not the 2 right?
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